Diagnosis and treatment of conditions affecting the brain are among the most difficult and complex problems that face the medical profession. The brain is a complex and delicate soft multi-component tissue structure that receives multiple inputs, processes these inputs, responds to the inputs and controls bodily functions through a complex neural network connected to the rest of the body through the spinal cord. The brain and spinal cord are contained within and protected by significant bony structures, e.g., the skull and the spine. Given the difficulty of safely accessing the areas of the brain housed within the hard bony protective skull, as well as navigating the delicate network and complex interactions that form the neural communication network contained within the brain that define the human body's ability to carry on its functions of speech, sight, hearing, functional mobility, reasoning, emotions, respiration and other metabolic functions, the diagnosis and treatment of brain disorders presents unique challenges not encountered elsewhere in the body.
For example, abnormalities such as intracranial cerebral hematomas (ICH), abscesses, glioblastomas (GB), metastases (mets) and functional diseases manifest themselves in the intraparenchymal subcortical space (i.e., the white matter) of the brain are particularly challenging to access, let alone treat. The white matter and the cortex contain eloquent communication structures (neural network) which are located in the subcortical space, called fiber tracts and fascicles which make up the fascicular anatomy. Thus, traditionally, unless the ICH, GB, and/or mets were considered anything but “superficial,” such conditions have been considered challenging to access or inoperable, simply because getting to the abnormality ICH, GB and/or mets are considered just as damaging as letting the condition take its course. Similarly, tissue abnormalities such as tumors, cysts and fibrous membrane growths which manifest within the intraventricular space of the brain are considered challenging to safely access and often inoperable, due to their locations within the brain and the eloquent real estate that must be traversed to access them.
In order to assist in diagnosis and subsequent treatment of brain disorders, clear, accurate imaging of brain tissue through the skull is required. In recent years significant advances have been made in imaging technology, including stereotactic X-ray imaging, Computerized Axial Tomography (CAT), Computerized Tomographic Angiography (CTA), Position Emission Tomography (PET) and Magnetic Resonance Imaging (MRI), sequences such as Diffusion Tensor Imaging (DTI) and Diffusion Weighted Images (DWI). Navigation systems (instrument position tracking systems) have also been improved to allow for the input of many of these improved imaging sequences such as CT and MRI to allow for improved accuracy when tracking instruments within the human body with the information downloaded to the navigational system from these imaging system sequences. These imaging devices and techniques permit the surgeon to observe conditions within the brain in a non-invasive manner without opening the skull, as well as provide a map of critical structures surrounding an area of interest, including structures such as blood vessels, membranes, tumor margins, cranial nerves, including the fascicular anatomy. If an abnormality is identified through the use of one or more imaging modalities and/or techniques, it may be necessary or desirable to biopsy or remove the abnormality. The navigational system allows for the intraoperative translation of these sequences during a procedure so that the user may maintain their intraoperative location and orientation during the case.
Once a course of action has been determined based upon one or more imaging techniques, a surgical treatment may be necessary or desired. In order to operate surgically on the brain, access must be obtained through the skull and eleoquent brain tissue containing blood vessels and nerves that can be adversely affected by even slight disturbances. Therefore, great care must be taken when traversing the internal corridor and operating on the brain so as not to disturb delicate blood vessels and nerves to prevent adverse consequences resulting from a surgical intervention.
Traditionally, accessing abnormalities which manifest in deeper spaces within the brain has meant a need for a surgery that creates a highly invasive approach. In some instances, in order to obtain access to target tissue, a substantial portion of the skull is removed and entire sections of the brain are retracted or removed to obtain access to deliver optics, light and instrumentation. For example, surgical brain retractors are used to pull apart or spread delicate brain tissue, which can leave pressure marks from lateral edges of the retractor. In some instances, a complication known as “retraction injury” may occur due to use of brain retractors. Of course, such techniques are not appropriate for all situations, and not all patients are able to tolerate and recover from such tissue disruptive invasive techniques.
It is also known to access certain portions of the brain by creating a burr hole craniotomy, but only limited surgical techniques may be performed through such smaller openings. In addition, some techniques have been developed to enter through the nasal passages, opening an access hole through the occipital bone to remove tumors located, for example, in the area of the pituitary, such as skull base tumors.
A significant advance in brain surgery is stereotactic surgery involving a stereotactic frame correlated to stereotactic X-ray images to guide a navigational system probe or other surgical instrument through an opening formed in the skull through brain tissue to a target lesion or other body. A related advance is frameless image guidance, in which an image of the surgical instrument is superimposed on a pre-operative image to demonstrate the location of the instrument to the surgeon and trajectory of further movement of the probe or instrument on or within the skull.
While minimally invasive and non-disruptive access systems have been developed now to provide access to previously difficult to access or what were previously considered inoperable areas in the brain and spine, many such access systems do not have the capability to provide navigational information during positioning of the access system.
Notwithstanding the foregoing advances in navigation technology of both frame and frameless stereotactic image guidance techniques, there remains a need for improved instrumentation of these navigational systems which allows for the use with new advances in minimally invasive access systems.